Since prostate cancer has become the number one male cancer, overtaking lung cancer, more and more males will be coming for evaluation of their prostate. Most men will have a DRE and a serum PSA level drawn before any further evaluation by diagnostic imaging such as transrectal ultrasound (TRUS). Two findings in this case are indications for performance of a TRUS with biopsy: (a) the presence of a focally abnormal area on the left side on DRE; and (b) an elevated PSA level of 16 ng/ml.
Prostate enlargement alone is not a reason for TRUS with or without biopsy unless the patient is symptomatic. After the age of 50, the prostate begins enlarging as a result of hyperplasia of tissues within the transition zone which is properly termed benign prostatic hyperplasia (BPH). This condition does not generally require treatment unless the patient becomes symptomatic. Unfortunately, the alterations in the DRE and the associated symptoms can mimic and mask the presence of prostate cancer. Because the clinical presentation can be confusing, attempts have been made to isolate cell specific markers such as Prostate Specific Antigen (PSA).
PSA is a glycoprotein liberated from the cytosol of prostatic acinar and ductal epithelium. The two commercially available assays, the Tandem R (Hybertech, Inc., San Diego, CA) and Pros Check (Yang Laboratories, Bellevue, WA), have different normal ranges given as 0-4 ng/ml and 0-2.5 ng/ml, respectively. In our case, the PSA level was abnormally elevated, but it is nonspecific since a rise may accompany cancer, inflammatory processes, and BPH. It has been proposed that a cut-off level >10 ng/ml or a PSA/prostate volume density >0.15 be surpassed before a patient is biopsied. Because of the nonspecificity of the absolute value of the PSA level, TRUS studies of the prostate have been performed to clarify the confusion.
Based on McNeal's histologic studies, the prostate is composed of glandular elements (2/3 volume) and nonglandular tissue or fibromuscular stroma (1/3 volume). The glandular tissue may be subdivided into a peripheral and central glands. The peripheral gland is further subdivided into the peripheral and central zones. The central or inner gland is composed of transitional zone and periurethral glandular tissue. Cancer arises most frequently from the peripheral zone (70%), transition zone (20%), and central zones (10%). Most commonly, cancers are imaged by TRUS as hypoechoic masses (70%) although cancers may be isoechoic (10-20%) or, very rarely, hyperechoic. The mass within the left peripheral gland is characteristic of a cancer. However, a differential exists with abnormalities such as focal prostatitis, prostatic intraepithelial neoplasia, scarring, and atrophy having a similar appearance.
More recently, investigators have used color Doppler to demonstrate increased flow within the tumor mass as a means of distinguishing a benign process from a malignant one. It is known that tumors are often supplied by tiny vessels, so-called tumor vessels. These vessels are lined by endothelium, lack a muscular coat and are surrounded by neoplastic cells. The blood flowing within them is very slow and low. It can be very difficult to detect, and the ability to identify it depends on machine related parameters such as frequency and wall filter settings. Unfortunately, increased flow may be seen with benign entities such as infection.
Therefore, ultrasound-guided transrectal biopsy is indicated for pathologic proof. The mass should be biopsied, but additional biopsies should be acquired because (a) the finding in question may not be the cancer, and (b) cancer is often a multifocal process. An accepted strategy is to perform a sextant biopsy sampling the basal portions of the ejaculatory ducts, medially at the midlevel of the prostate and at the apices, bilaterally.
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